The Science Case

Science with a 30-Meter Telescope

A 30-meter telescope, operating in wavelengths ranging from the ultraviolet to the mid-infrared, is an essential tool to address questions in astronomy ranging from understanding star and planet formation to unraveling the history of galaxies and the development of large-scale structure in the universe.

The 30-meter aperture permits the telescope to focus more sharply than smaller telescopes by using the power of diffraction of light. The large aperture also collects more light than smaller scopes, allowing images of fainter objects. TMT will therefore reach further and see more clearly than previous telescopes by a factor of 10 to 100 depending on the observation.

In addition to providing nine times the collecting area of the current largest optical/infrared telescopes (the 10-meter Keck Telescopes), TMT will be used with adaptive optics systems to allow diffraction-limited performance, i.e., the best that the optics of the system can theoretically provide. This will provide unparalleled high-sensitivity spatial resolution more than 12 times sharper than what is achieved by the Hubble Space Telescope. For many applications, diffraction-limited observations give gains in sensitivity that scale like the diameter of the mirror to the fourth power, so this increase in size has major implications.

TMT will provide new observational opportunities in essentially every field of astronomy and astrophysics. Because of the decades-long lifetime of TMT and the often-rapid advancement of astronomy into new areas, broadly useful capabilities have been emphasized, while maintaining specific capabilities needed to address key programs that are known now.

TMT will be a fundamental tool for investigating a very wide range of topics, including

Spectroscopic exploration of the “dark ages” when the first sources of light and the first heavy elements in the universe formed and when the universe, which had recombined at redshift (z) ~1000, became re-ionized by these sources of light. The nature of “first-light” objects and their effects on the young universe are among the outstanding open questions in astrophysics. Here TMT and the James Webb Space Telescope (JWST) will work hand-in-hand, with JWST providing the targets for detailed study with TMT’s spectrometers.

Exploration of galaxies and large-scale structure in the young universe, including the era in which most of the stars and heavy elements were formed and the galaxies in today’s universe were assembled. TMT will allow detailed spectroscopic analysis of galaxies and subgalactic fragments during the epoch of galaxy assembly. Observations with TMT will help answer questions about the early production and dispersal of the chemical elements, the distribution of baryons within dark matter halos and the processes of hierarchical merging of subgalactic fragments.

The early epoch of the formation and development of the large-scale structures that dominate the universe today should also be observable with the TMT. Studies of the matter power spectrum on small spatial scales, using direct observations of distant galaxies and the intergalactic medium (IGM), provide information on the physics of the early universe and the nature of dark matter that are inaccessible using any other techniques.

Investigations of massive black holes throughout cosmic time. The recently-discovered tight correlation between central black hole mass and stellar bulge velocity dispersion strongly implies that black hole formation and growth is closely tied to the processes that form galaxies. This result also suggests that super massive black holes are at the centers of most or all large galaxies. The TMT combination of high spatial resolution and moderate-to-high spectral resolution will extend our capability to detect and investigate central black holes to cosmological distances. In addition to investigations designed to understand the black hole-galaxy growth issue, nearby supermassive black holes can be analyzed with very high physical resolution. This will allow us to measure general relativistic effects at the center of the Galaxy and to spatially resolve the accretion disks for active black holes in the centers of galaxies to the distance of the Virgo cluster.

Exploration of planet-formation processes and the characterization of extra-solar planets. Two of the most exciting challenges to astrophysics in the next decades are to understand the physical processes that lead to star and planet formation and to characterize the properties of extra-solar planets. TMT will have a very important role to play in many aspects of this endeavor.

Spectroscopic discovery observations that push into the terrestrial-planet regime, the kinematics of proto-planetary disks, spectroscopic detection and analysis of extra-solar planet atmospheres and the direct detection of extra-solar planets in reflected and emitted light are all goals that are driving the TMT design requirements.

Furthermore, as has been the case for every previous increase in capability of this magnitude, it is very likely that the scientific impact of TMT will go far beyond what we envision today and TMT will enable discoveries that we cannot anticipate.

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Numerical simulation illustrating the web of intergalactic gas threading the early universe. TMT has enough lightgathering power to use faint, distant galaxies as probes to detect intervening intergalactic gas, and to discover the interplay in dynamics and chemical composition between this gas and the first generations of stars in nascent galaxies.Image courtesy: L. Hernquist

A numerical simulation of a planet-forming disk. The “gaps” produced by the gravitational effects of forming planets can be inferred by exploiting the light gathering power of TMT to feed a sensitive infrared spectrograph capable of “deconstructing” the structure of the disk. Image courtesy: University of Washington High Performance Computing Center.